The present disclosure relates to human body communication, and more particularly, to a receiver for human body communication and a method for removing a noise thereof for removing a radiation noise radiated from the receiver itself in order to raise reception performance of a signal received by using a human body as a medium and stably recovering a signal having been transmitted from a transmitter.
Since transmission/reception of a signal using a human body as a medium does not require a transmission line of high conductivity for signal transmission, it is difficult to eavesdrop on the signal, and high frequency generation for wireless transmission, a modulator and a demodulator are not necessary. Thus the human body communication is a method of signal transmission which has a simple structure and operates with low power consumption. Since the signal transmission/reception using a human body as a medium uses a transmission medium having low conductivity due to nature of the human body medium, an analog amplifier having a very high gain is typically necessary to receive and recover a signal. In addition, since the human body itself operates as an antenna and thus surrounding noises absorbed from surroundings are added to a signal having been transmitted from a transmitter and the resulted signal is received by a receiver, the receiver is typically provided with a band pass filter for passing only the signal having been transmitted from the transmitter and filtering out unnecessary noises, and recovers the original transmitted data.
On the other hand, a clock is necessary for operation of a digital modem for data transmission between a transmitter and a receiver, and the clock operates on the basis of an identical frequency for synchronization of transmission/reception. However, since each of the transmitter and receiver uses an independent frequency oscillator, minute frequency and phase errors occur and in order to remove such frequency and phase errors, a clock and data recovery circuit in the receiver recovers a clock precisely synchronized with a frequency of the transmitter and the receiver uses the clock.
Accordingly, the receiver operates, transmission/reception synchronization is achieved, and then data is recovered on the basis of a frequency identical to an operation frequency of the transmitter and a transmission rate of a digital data signal flowing into the human body from the transmitter. In other words, since the receiver uses the same frequency band as that of the transmitter, a digital noise generated in the receiver is radiated in the air and flowed into human epidermis adjacent to a position on which the receiver is attached, a band pass filter in the receiver does not filter out the flowed digital noise induced by the receiver, and thus only a corresponding frequency band signal is amplified at the moment when passing an analog amplifier of a high gain. Accordingly, when the analog amplifier of a high gain is used, oscillation occurs at a sync frequency of the transmitter/receiver and a signal having been transmitted from the transmitter may not be recovered.